In recent years, precision machining technologies and precision servo control technologies play vast important rules with the rapid growth of the computer information and electrics industries. Traditionally, DC or AC servo motors operated with screws are applied in most precision positioning systems to achieve the purpose of precision positioning. For example, by using piezoelectric actuator at 10 micrometer motion distance which can reach high precision of 10 nanometers (nm), and the piezoelectric actuator can also meet a rapid reacting request. However, the superior limit of piezoelectric actuator is the moving range. It can not be used if there needs a larger moving range condition. In order to meet the long distant request, most of them utilize server motor with screw bar or directly utilize linear motors in tradition. Nonetheless, it renders the whole positioning precision down because of backlash of screw bar and friction of bearings. Linear motors also influenced by the ripple and end effect which reduce the positioning precision.
In general, a method to solve said friction is not only strengthening the manufacture precision of the system hardware, but also lubricating oil which can reduce the friction. Furthermore, it utilizes many kind of ways to estimate the friction under controlling principle and utilizes reverse force to against the friction effect.
In millimicron semiconductor fabricating process, it has reached certain level of technology level. At 0.9 μm fabricating process, its surface examining technology will play an important role. Although it can use the method of reducing friction method which has mentioned above to the examining, but it would render the examining results imprecise due to the electrostatic or shift accuracy down by few friction. It's obvious that none-contacting force is a better way to solve the system problem above. Aerodynamic suspension system, electrostatic suspension system and maglev system are common examples which use none-contacting force. However, the first two are not suitable in some particular environment, e.g. clean room, vacuum room, etc. Therefore, in order to develop a positioning system with high accuracy and be able to use in many environments, a system which utilizes maglev theorem to be basic construction has been developed. Beyond the mature technologies of double axles maglev technology recently, Dr. Trumper, from MIT. USA, has published 6 DOF maglev positioning system which utilizes linear motors as basic construction that also provides vertical maglev and lateral impellent that the system needs at 1996. However, it is not easy to apply to relate industries for its complexity and difficulty.
Moreover, Dr. Trumper's student Kim, at Texas University, has designed a new 6 DOF micro-actuator which is still under developing. The system utilizes coils and permanent magnets to achieve 6 DOF motion. Although it is a high precision system, but it does not suit in large movement application for its hardware design. Kwang and Yoon, from Korea, have developed a construction that utilizes switching two dimensional electromagnet arrays and regulating current for rendering the platform moving on a plane. However, it still could not surmount the boundary problem between coils. On the other hand, it also means that it could not reach the large movement request.
Moreover, according to the disadvantage of the used maglev positioning systems, the inventor has invented a new planer maglev positioning system which could achieve large moving range and high 6 DOF moving accuracy.